Dry friction clutch/brakes depend upon the rubbing of a dry friction material against dry reaction members to start and stop a press. This continuous dry rubbing causes wearing of both the friction material and the reaction members as well as causing the generation of heat in these members. The faster the press operates and the faster the flywheel rotates, greater is the amount of wear and heat which are generated. This generation of wear and heat requires periodic gap adjustment between the friction plates and the reaction members to keep the clutch/brakes functioning and the press operating correctly. The trip rate or cycle speed of a press equipped with a dry friction clutch/brake unit is limited because the mass of the unit determines its heat dissipation capacity. If the mass of the unit is increased to increase its heat dissipation capacity, the inertia that must be started and stopped is also increased. These factors define a closed loop from which it is impossible to escape when trying to substantially increase the performance of the system.
Oil shear brake and clutch units have been developed to eliminate the problems associated with the dry friction type of units. The oil shear systems use hydraulic actuation instead of air actuation and the units have been developed with key modules which can be easily adapted to be mated with the various types of presses. Properly designed oil shear clutch/brake drives offer the advantage of little or no wear of plates in the disk stacks and no brake fade. This provides a more precise operation of the press and dramatically increases press up-time. The oil film between the adjacent disks carries the heat generated by the start-stops of the unit away from the disk stacks. This removal of heat offers the advantage that there is now no practical limit for the press trip rate and the flywheel speed. In addition, this removal of heat provides unlimited inching capabilities.
While these oil shear clutch/brake drive units have significantly improved the operation of the units, they have all been supplied as single units which have the clutch and brake units interfaced using various techniques for the engagement and disengagement of the clutch and for the application and release of the brake. The various techniques for the operation of the clutch and brake units operation have all been directed toward the problem of providing a specified amount of overlap between the two units. Accordingly, what is needed is a versatile press drive system which incorporates the flexibility to be applied to a wider variety of presses where size and performance of the press drive system are of the utmost importance. In addition, the press drive system should simplify the coordination and operation of the brake and clutch units while keeping the press drive system at reasonable cost levels.